The present invention relates to an electromagnetic trip device for an electric switch apparatus comprising a magnetic circuit formed by a shell, a fixed core and a moving core sliding due to the action of a coil. The moving core has a radial crown separating a first part and a second part of different radial cross-sections, the shell comprising a radial surface having an opening through which the first part of the moving core passes. Superposition of the radial crown of the moving core and of the radial surface of the shell, in a rest position, forms a magnetic flux transfer surface enabling the flow of an axial magnetic flux.
The present invention also relates to an electric protective switch apparatus provided with at least one movable contact operating in conjunction with at least one stationary contact.